Go Down

Topic: Buzzer Circuit (Read 3 times) previous topic - next topic


I would like to build a simple buzzer circuit which beeps for some 5sec then die off when AC power comes on. I know circuit is kinda simple but i cant seem to figure out  :( here is wat  I came up with...
AC to DC rectification (say 6v)
then a capacitor in series with resistor in series with a peizo buzzer...
like capacitor take time to charge till that time peizo buzzer is on after that once capacitor charges fully to max voltage peizo dies off...
I am i doing this the right way? or is there a better way to do it...
Plz do help out. I want to minimise the component count for this.
I keep feeling its such a simple circuit but I just cant figure out how to....  :'(


With an Arduino one could make one outputpin HIGH for five seconds in setup() when you want a nice "die off"consider digitalWrite(). see http://arduino.cc/en/Tutorial/AnalogInOutSerial, to get started.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


It not power failure circuit. just the opposite. the buzzer should sound say for 5sec then die off. just to let me know that AC power is back.
With Arduino I can simply do this. but come on for such an easy task I don't think I need to use Arduino.
Any idea if the circuit i explained will work? My house is currently under renovation so I cant actually practically work on this for a week. Thats why I cant implement this currently and see if it works.  :(


Nov 02, 2010, 02:55 am Last Edit: Nov 02, 2010, 03:03 am by CrossRoads Reason: 1
So really want the AC going thru a relay that is Normally closed, and have some of that same AC be rectified into a low level DC (say by having the same AC drive a cheap wallwart as a 5V/12V source) , and have wallwart DC output go thru a current limit resistor to charge up a cap and eventually drive the relay into the open state to turn off the AC to your alarm bell.
System resets on power loss.

Shouldn't be that hard.

alarm bell:
(or just a cheap radio turned up really loud!)
wallwart power supply to drive relay (or as needed for the relay you pick)
resistor & capacitor from your favorite supplier such that 1/2PiRC = 5 seconds (or something like that, maybe need a square root of 2 or something in there too, I'm a digital guy, go google it - big cap, small R)
(is it just me, or is turn-on current/voltage not shown on the data sheet?)

Okay, this one is simple to follow
5V across coils, 120V across the relay itself, good 1A (for that 125W radio, good & loud!)

Don't forget another R in parallel with cap to ground to make sure it bleeds off on a timely manner.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.


Nov 04, 2010, 03:11 am Last Edit: Nov 04, 2010, 03:15 am by dev_000 Reason: 1
This circuit will work? Its Buzzer which works at around 4V.
Shouldn't I add something to discharge the cap???

Go Up